1. Field of the Invention
The present invention relates to a control for a vehicular powertrain comprising a fuel-controlled engine and a multiple-ratio drivetrain, including a multiple-speed mechanical transmission and a single- or multiple-speed drive axle assembly. In particular, the present invention relates to a powertrain control wherein the in-gear position of the shift actuator and the engine torque is monitored and, if the in-gear position indicates a less than fully engaged jaw clutch condition and if the engine torque is low, the jaw clutch is urged into full engagement.
2. Description of the Prior Art
Vehicular drivetrains including multiple-speed mechanical transmissions, usually compound transmissions, or simple transmissions coupled with multiple-speed axles, having 7, 9, 10, 13, 16, 18 or more forward speed ratios, are well known in the prior art, especially for heavy-duty vehicles, as may be seen by reference to U.S. Pat. Nos. 5,370,013; 5,527,237 and 4,754,665, the disclosures of which are incorporated herein by reference. Both synchronized and non-synchronized jaw clutches are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 5,546,823; 5,588,516 and 5,642,643, the disclosures of which are incorporated herein by reference.
Control systems and methods for calculating engine output torque (also called "flywheel torque") are known in the prior art, as may be seen by reference to U.S. Pat. No. 5,509,867, the disclosure of which is incorporated herein by reference.
Automated and manual transmission systems wherein engine output torque is controlled and/or limited as a function of engaged gear ratio and/or vehicle speed are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 5,477,827; 5,797,110; 5,457,633; 4,889,014; 5,738,606; 5,679,096 and 5,876,302, the disclosures of which are incorporated herein by reference. As is known, modern vehicular powertrains usually include electronically controlled engines, which may be controlled as to engine speed and/or engine torque. By way of example, according to the SAE J-1939 data link protocol, commands may be issued to the engine for fueling of the engine in accordance with (a) driver's fuel demand, (b) a requested engine speed, (c) a requested engine torque and/or (d) a requested maximum engine torque and/or engine speed.
While the prior art systems are effective to maintain an in-gear condition, the use of detents and/or constant urging in higher force actuators being required may result and/or undue wear on the shifting mechanism. In particular, the prior art includes systems having an in-gear detents for maintaining an in-gear condition. While effective, detents are not totally satisfactory as they require higher shift forces and may slow shifts. The prior art also includes systems which, upon sensing a partial disengagement, will urge jaw clutches towards full engagement. These systems are not totally satisfactory as force was applied to the shifting mechanism during torque lock, conditions which might result in undue wear and/or damage.